When a steel strip is subjected to a metal working or fabrication operation, such as a temper rolling process, it is desirable for the steel strip to have a film of lubricant thereon to facilitate the particular operation. Generally, the lubricant film can be either solid or liquid. Particularly in a temper mill, liquid lubricants have certain advantages, and dry lubricants have other advantages. Steel strip can be temper rolled at a faster rate using a dry lubricant film, and dry lubricant films provide for more exact transfer of the surface texture of temper mill working rolls to the surface of the steel strip. Further, dry lubricants permit the use of automatic shape correction apparatus used as a step in the temper rolling process to assure a flat, uniform surface on the steel strip.
On the other hand, there are advantages to using a wet lubricant film during the temper rolling process. One advantage of wet lubricants for the temper rolling process is in providing more lubricity to the surface of the steel strip, thereby permitting the use of a greater force against the steel strip by the working rolls of the temper mill, resulting in increased stretchability of the resulting steel strip, and/or requiring less interstand tension in a two-stand temper mill, or less back-up tension in a single-stand temper mill. Another substantial advantage of using a wet lubricant during the temper rolling of steel strip is that wet lubricants can be applied to the surface of the steel strip under fluid pressure sufficient to remove much of the dust, dirt and other contaminants that may be on the surface of the steel strip entering the temper mill. Such contaminants are picked up by the surfaces of the working rolls of the temper mill using extant dry lubricant films. Any defects imparted to the surface of the temper mill working rolls are imparted to the surface of temper rolled steel strip. As a result, contaminant-carrying working rolls must be replaced periodically. Using a wet lubricant film during temper milling has the advantage of much less frequent replacement of the temper mill working rolls, e.g., 10-25 rolls of steel strip can be temper rolled without temper mill working roll replacement versus about 6 rolls of steel strip using extant dry lubricants.
Wet lubricants, however, have other disadvantages, such as either requiring a substantial amount of organic liquid solvent for completely coating the steel strip, thereby presenting a fire hazard; or with the use of water as the wet lubricant carrier, aqueous lubricant compositions are detrimental to corrosion resistance properties.